1. Field of the Invention
This invention relates to an improved fluid flow sensing switch device and method of making the same as well as to fuel control system utilizing such device for controlling the operation of electrical ignition means for a burner means of the fuel control system.
2. Prior Art Statement
It is known to applicant to provide a fluid flow sensing switch device having a housing means provided with a fluid flow passage therethrough defined by an inlet and outlet separated by a valve seat controlled by a movable valve member that is operated by a pressure differential between the inlet and the outlet acting on a flexible diaphragm carried by the housing means, the device having an electrical switch construction operatively associated with the valve member and having contact means thereof disposed in the fluid flow passage so as to be exposed to fluid flow therethrough and being actuated by the pressure differential acting on the flexible diaphragm.
For example, see the following copending U.S. patent application:
1. Ser. No. 936,112, filed Aug. 23, 1978.
The fluid flow sensing switch device of item (1) above has one contact of the electrical switch construction carried by the flexible diaphragm, that actuates the switch construction and the movement of the valve member by sensing the pressure differential between the inlet and the outlet across the same, and has the other contact of the switch construction carried on the valve member to be contacted by the diaphragm contact when the diaphragm moves its contact against the valve member carried contact so that the switch construction will be closed before the diaphragm can move the valve member to an open position thereof.
It is also known to applicant to provide an electronic switching circuit to be controlled by the switch construction of such a fluid flow sensing switch device so that a relatively small current flow can be controlled by the switch construction of the fluid flow sensing switch device to eliminate any buildup of carbon on the contacts thereof while permitting the electronic switching means to control a large current flow for operating the burner ignition means.
For example, see the following copending U.S. patent application:
(2) Ser. No. 936,116, filed Aug. 23, 1978.
The electronic switching circuit of item (1) is located external to the fluid flow sensing switch device that carries the switch construction for operating such electronic switching means.